Traditional hot melt materials that are used in the art for reinforcement of structural members, such as hem flange joints, have several limitations. Generally speaking, the prior art materials require adhesion enhancement, mechanical fasteners, and/or pressurization for placement in the desired location. These prior art methods also may initiate re-melt flow upon exposure to heat, either unexpectedly or inadvertently, thereby reducing their ability to provide structural reinforcement and, more importantly, corrosion protection to the structural members at the desired location at a desired time and place during the manufacturing process. Additionally, standard application of traditional hot melt materials may expose uncoated portions of structural members to corrosion and reduce their structural integrity. For example, the standard application generally requires the traditional hot melt material to be dispensed into the radius of the outer panel of a hem flange joint. Thereafter, the inner panel of the hem flange joint is inserted or otherwise placed into contact in the area of the outer panel. The two panels are then crimped together and pass through a gel oven to partially cure the traditional hot melt material so that it does not wash off during the cleaning and electrodeposition coating processes (e-coat). These methods and traditional hot melt material found in the prior art is at least partially cured while passing through the electrodeposition coating process and the paint ovens typically encountered in the manufacturing environment. Generally speaking, the current materials, methods, and processes found in the prior art incorporate the use of a hem flange adhesive (i.e. the material that is squeezed out or otherwise expelled from the selected flange) and a wax stick material that is disposed within or coats the interior of the selected flange.
However, these prior art materials and processes have a number of drawbacks and deficiencies which can ultimately diminish their efficiency and performance in a manufacturing facility. For example, during standard application before the electrodeposition coating process, metal shavings, oil and other types of contamination can be trapped in the hem flange joint or some other targeted portion of a transportation vehicle or joint to be reinforced, which can cause electrodeposition coating not to adhere to the metal surface of the hem flange joint very well, thereby producing a site for corrosion initiation. Moreover, the crimping process found in the prior art may serve to inhibit the flow or disposition of the selected material (including e-coat) within the joint or flange, since the now crimped panel can function as a barrier to proper flow of the materials, thereby leading to corrosion over time. Corrosion can also occur when too much standard hot melt material is dispensed into the outer panel of hem flange joint. The excess standard hot melt material is expelled during the crimping process and may flow onto the hem flange panels and lead to unwanted hem flange adhesive and wax stick materials being deposited into the flange and surrounding areas which can impede melt and sealing and lead to corrosion over the life of the vehicle. This excess standard hot melt material is difficult to clean, thereby causing maintenance issues to arise in the manufacturing facility. It can also result in inadequate adherence between the electrodeposition coating and the hem flange panels, thereby producing sites for corrosion initiation. Accordingly, both an over abundance and a lack of proper placement of sufficient amounts of hot melt material within the selected joint can interfere with the e-coat process and lead to the development of corrosion areas within the vehicle over time. Another limitation of the techniques found in the prior art is that the amount of traditional hot melt material being dispensed into the outer panel of hem flange joint may be inconsistent and non-uniform. As discussed above, when there is too much traditional hot melt material dispensed, corrosion may occur as a result of poor e-coat deposition. Likewise, if an insufficient amount of traditional hot melt material is dispensed into a flange or joint, corrosion is also likely to occur since a gap or gaps of dispersed material may develop during e-coat deposition resulting in uncoated metal in the hem flange.
Accordingly, the present application overcomes the drawbacks and disadvantages found in the prior art materials and processes by providing a single product structural hot melt material which satisfies the need in industry and manufacturing operations for a structural material that can be directly applied to a particular application without mechanical fasteners/or pressurization in order to reinforce a chosen structural member, joint, or flange. There is also a need for an improved structural material that provides better mechanical performance and is a thermoset hot melt, which does not flow upon re-heating. Additionally, there is a need for an improved structural material that can be inserted, applied, or otherwise disposed into contact with portions of a land, marine, or aerospace vehicle in a manner that prevents corrosion. By providing a structural material with better mechanical properties and desirable processing attributes, the present invention addresses and overcomes the shortcomings found in the prior art.